Rationale: The overall goal of this application is to advance the science of diagnostic error reduction. Diagnostic error (defined as the failure to provide the patient with an accurate and timely diagnosis or to communicate that explanation to the patient) is an important, common, and costly problem. These errors and their impact on patient outcomes, however, have been underemphasized until recently. Increased attention is now being paid to the problem as evidenced by the publication of the Institute of Medicine report Improving Diagnosis in Health Care. Much, however, remains to be learned about the best way to identify and measure these errors as well as what interventions are most likely to prevent them. Understanding the complex origins of diagnostic errors requires a multidisciplinary approach that coordinates the input of clinicians, educators, human factors experts, and cognitive scientists, as well as participation of important stakeholders such as payers, patient advocates, and accrediting/credentialing organizations. Previous Conferences and Impact: Previous conferences, all supported by AHRQ, provided forums for groundbreaking research as well as a means of bringing together researchers and experts to focus on issues that lie at the intersection of diagnostic reasoning and medical error. These prior meetings have had a significant impact on the field as a whole including the formation of a new organization (Society to Improve Diagnosis in Medicine) and the publication of multiple high-impact and influential papers. Conference Plan: The conference will be a 3.5-day meeting. The first day will center on summits designed to bring together key leaders in specific areas of the study of diagnostic error with research, patient and educational summits all planned. The subsequent conference will focus on the impact of the IOM report, including discussion and dissemination of the advances that have improved diagnostic performance and patient safety following the IOM report. There will be a concentration on promulgating interventions demonstrated to effect an improvement in diagnostic safety. An emphasis will placed on sharing research advances and delineating a research agenda. Attention will also be devoted to procurement of grants and funding, and promoting research capacity. Speakers will be internationally recognized leaders from diverse disciplines including cognitive psychology, patient engagement, educational reform and patient safety. Impact/ Deliverables: The conference will provide a forum to establish research priorities in the field, develop educational curricula and foster interdisciplinary collaboration. The ultimate goal of the conference is the development and dissemination of strategies to reduce diagnostic errors that may be widely implemented.